From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EC0FCC7618F for ; Mon, 22 Jul 2019 15:58:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B7FC9218EA for ; Mon, 22 Jul 2019 15:58:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729049AbfGVP6V (ORCPT ); Mon, 22 Jul 2019 11:58:21 -0400 Received: from retiisi.org.uk ([95.216.213.190]:56518 "EHLO hillosipuli.retiisi.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728154AbfGVP6V (ORCPT ); Mon, 22 Jul 2019 11:58:21 -0400 Received: from valkosipuli.localdomain (valkosipuli.retiisi.org.uk [IPv6:2a01:4f9:c010:4572::80:2]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by hillosipuli.retiisi.org.uk (Postfix) with ESMTPS id 2E862634C87; Mon, 22 Jul 2019 18:58:15 +0300 (EEST) Received: from sailus by valkosipuli.localdomain with local (Exim 4.92) (envelope-from ) id 1hpaha-0000Qa-Eg; Mon, 22 Jul 2019 18:58:14 +0300 Date: Mon, 22 Jul 2019 18:58:14 +0300 From: Sakari Ailus To: Nishka Dasgupta Cc: Paul Kocialkowski , Jeremy Sowden , maxime.ripard@bootlin.com, mchehab@kernel.org, gregkh@linuxfoundation.org, wens@csie.org, linux-media@vger.kernel.org, devel@driverdev.osuosl.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v2] staging: media: sunxi: Add bool cast to value Message-ID: <20190722155814.GC1263@valkosipuli.retiisi.org.uk> References: <20190722060651.6538-1-nishkadg.linux@gmail.com> <20190722111225.GA2695@azazel.net> <20190722122438.GA1908@aptenodytes> <45555499-57f3-a315-6f84-f878c3aa0130@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <45555499-57f3-a315-6f84-f878c3aa0130@gmail.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org On Mon, Jul 22, 2019 at 07:14:08PM +0530, Nishka Dasgupta wrote: > On 22/07/19 5:54 PM, Paul Kocialkowski wrote: > > Hi, > > > > On Mon 22 Jul 19, 12:12, Jeremy Sowden wrote: > > > On 2019-07-22, at 11:36:51 +0530, Nishka Dasgupta wrote: > > > > Typecast as bool the return value of cedrus_find_format in > > > > cedrus_check_format as the return value of cedrus_check_format is > > > > always treated like a boolean value. > > > > > > > > Signed-off-by: Nishka Dasgupta > > > > --- > > > > Changes in v2: > > > > - Add !! to the returned pointer to ensure that the return value is > > > > always either true or false, and never a non-zero value other than > > > > true. > > > > > > > > drivers/staging/media/sunxi/cedrus/cedrus_video.c | 2 +- > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > > > diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_video.c b/drivers/staging/media/sunxi/cedrus/cedrus_video.c > > > > index e2b530b1a956..b731745f21f8 100644 > > > > --- a/drivers/staging/media/sunxi/cedrus/cedrus_video.c > > > > +++ b/drivers/staging/media/sunxi/cedrus/cedrus_video.c > > > > @@ -86,7 +86,7 @@ static struct cedrus_format *cedrus_find_format(u32 pixelformat, u32 directions, > > > > static bool cedrus_check_format(u32 pixelformat, u32 directions, > > > > unsigned int capabilities) > > > > { > > > > - return cedrus_find_format(pixelformat, directions, capabilities); > > > > + return !!(bool)cedrus_find_format(pixelformat, directions, capabilities); > > > > } > > > > > > I think the original was fine. The return value of cedrus_find_format > > > will be automatically converted to bool before being returned from > > > cedrus_check_format since that is the return-type of the function, and > > > the result of converting any non-zero value to bool is 1. > > > > Okay I was a bit unsure about that and wanted to play it on the safe side > > without really looking it up, but that gave me the occasion to verify. > > > > From what I could find (from my GNU system's /usr/include/unistring/stdbool.h): > > > > Limitations of this substitute, when used in a C89 environment: > > > > - In C99, casts and automatic conversions to '_Bool' or 'bool' are > > performed in such a way that every nonzero value gets converted > > to 'true', and zero gets converted to 'false'. This doesn't work > > with this substitute. With this substitute, only the values 0 and 1 > > give the expected result when converted to _Bool' or 'bool'. > > > > So since the kernel is built for C89 (unless I'm mistaken), I don't think the > > compiler provides any guarantee about bool values being converted to 1 when > > they are non-zero. As a result, I think it's best to be careful. > > > > However, I'm not sure I really see what cocinelle was unhappy about. You > > mentionned single-line functions, but I don't see how that can be a problem. > > It's not a problem per se. I'm just working on a cleanup project for which I > went through all of staging replacing single-line functions with what they > were calling. In some cases that makes it easier to figure out what a > particular function call does, since the called function actually does > something itself instead of just calling a different function? > This function was also flagged as one such potentially-removable function by > Coccinelle; but in order to do the same replacement that I'd done in other > staging drivers, I thought I would do something about the type mismatch > first, especially since find_format doesn't appear to be used anywhere else. > However, now I won't remove check_format and replace it with find_format as > I'd originally planned, since you've said that isn't necessary here. That > leaves the return type issue. > > > > So in the end, I think we should keep the !! and drop the (bool) cast if there's > > no particular warning about it. > > Should I send a version 3 that does this? bool was introduced in C99. Converting a non-zero value to boolean will yield true as a result. Please keep the code as-is; it's much easier to read that way. -- Kind regards, Sakari Ailus From mboxrd@z Thu Jan 1 00:00:00 1970 From: sakari.ailus@iki.fi (Sakari Ailus) Date: Mon, 22 Jul 2019 18:58:14 +0300 Subject: [PATCH v2] staging: media: sunxi: Add bool cast to value In-Reply-To: <45555499-57f3-a315-6f84-f878c3aa0130@gmail.com> References: <20190722060651.6538-1-nishkadg.linux@gmail.com> <20190722111225.GA2695@azazel.net> <20190722122438.GA1908@aptenodytes> <45555499-57f3-a315-6f84-f878c3aa0130@gmail.com> Message-ID: <20190722155814.GC1263@valkosipuli.retiisi.org.uk> List-Id: Linux Driver Project Developer List On Mon, Jul 22, 2019@07:14:08PM +0530, Nishka Dasgupta wrote: > On 22/07/19 5:54 PM, Paul Kocialkowski wrote: > > Hi, > > > > On Mon 22 Jul 19, 12:12, Jeremy Sowden wrote: > > > On 2019-07-22,@11:36:51 +0530, Nishka Dasgupta wrote: > > > > Typecast as bool the return value of cedrus_find_format in > > > > cedrus_check_format as the return value of cedrus_check_format is > > > > always treated like a boolean value. > > > > > > > > Signed-off-by: Nishka Dasgupta > > > > --- > > > > Changes in v2: > > > > - Add !! to the returned pointer to ensure that the return value is > > > > always either true or false, and never a non-zero value other than > > > > true. > > > > > > > > drivers/staging/media/sunxi/cedrus/cedrus_video.c | 2 +- > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > > > diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_video.c b/drivers/staging/media/sunxi/cedrus/cedrus_video.c > > > > index e2b530b1a956..b731745f21f8 100644 > > > > --- a/drivers/staging/media/sunxi/cedrus/cedrus_video.c > > > > +++ b/drivers/staging/media/sunxi/cedrus/cedrus_video.c > > > > @@ -86,7 +86,7 @@ static struct cedrus_format *cedrus_find_format(u32 pixelformat, u32 directions, > > > > static bool cedrus_check_format(u32 pixelformat, u32 directions, > > > > unsigned int capabilities) > > > > { > > > > - return cedrus_find_format(pixelformat, directions, capabilities); > > > > + return !!(bool)cedrus_find_format(pixelformat, directions, capabilities); > > > > } > > > > > > I think the original was fine. The return value of cedrus_find_format > > > will be automatically converted to bool before being returned from > > > cedrus_check_format since that is the return-type of the function, and > > > the result of converting any non-zero value to bool is 1. > > > > Okay I was a bit unsure about that and wanted to play it on the safe side > > without really looking it up, but that gave me the occasion to verify. > > > > From what I could find (from my GNU system's /usr/include/unistring/stdbool.h): > > > > Limitations of this substitute, when used in a C89 environment: > > > > - In C99, casts and automatic conversions to '_Bool' or 'bool' are > > performed in such a way that every nonzero value gets converted > > to 'true', and zero gets converted to 'false'. This doesn't work > > with this substitute. With this substitute, only the values 0 and 1 > > give the expected result when converted to _Bool' or 'bool'. > > > > So since the kernel is built for C89 (unless I'm mistaken), I don't think the > > compiler provides any guarantee about bool values being converted to 1 when > > they are non-zero. As a result, I think it's best to be careful. > > > > However, I'm not sure I really see what cocinelle was unhappy about. You > > mentionned single-line functions, but I don't see how that can be a problem. > > It's not a problem per se. I'm just working on a cleanup project for which I > went through all of staging replacing single-line functions with what they > were calling. In some cases that makes it easier to figure out what a > particular function call does, since the called function actually does > something itself instead of just calling a different function? > This function was also flagged as one such potentially-removable function by > Coccinelle; but in order to do the same replacement that I'd done in other > staging drivers, I thought I would do something about the type mismatch > first, especially since find_format doesn't appear to be used anywhere else. > However, now I won't remove check_format and replace it with find_format as > I'd originally planned, since you've said that isn't necessary here. That > leaves the return type issue. > > > > So in the end, I think we should keep the !! and drop the (bool) cast if there's > > no particular warning about it. > > Should I send a version 3 that does this? bool was introduced in C99. Converting a non-zero value to boolean will yield true as a result. Please keep the code as-is; it's much easier to read that way. -- Kind regards, Sakari Ailus From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AF17DC7618F for ; Mon, 22 Jul 2019 16:00:48 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 7E67E218EA for ; Mon, 22 Jul 2019 16:00:48 +0000 (UTC) Authentication-Results: mail.kernel.org; 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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Jul 22, 2019 at 07:14:08PM +0530, Nishka Dasgupta wrote: > On 22/07/19 5:54 PM, Paul Kocialkowski wrote: > > Hi, > > > > On Mon 22 Jul 19, 12:12, Jeremy Sowden wrote: > > > On 2019-07-22, at 11:36:51 +0530, Nishka Dasgupta wrote: > > > > Typecast as bool the return value of cedrus_find_format in > > > > cedrus_check_format as the return value of cedrus_check_format is > > > > always treated like a boolean value. > > > > > > > > Signed-off-by: Nishka Dasgupta > > > > --- > > > > Changes in v2: > > > > - Add !! to the returned pointer to ensure that the return value is > > > > always either true or false, and never a non-zero value other than > > > > true. > > > > > > > > drivers/staging/media/sunxi/cedrus/cedrus_video.c | 2 +- > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > > > diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_video.c b/drivers/staging/media/sunxi/cedrus/cedrus_video.c > > > > index e2b530b1a956..b731745f21f8 100644 > > > > --- a/drivers/staging/media/sunxi/cedrus/cedrus_video.c > > > > +++ b/drivers/staging/media/sunxi/cedrus/cedrus_video.c > > > > @@ -86,7 +86,7 @@ static struct cedrus_format *cedrus_find_format(u32 pixelformat, u32 directions, > > > > static bool cedrus_check_format(u32 pixelformat, u32 directions, > > > > unsigned int capabilities) > > > > { > > > > - return cedrus_find_format(pixelformat, directions, capabilities); > > > > + return !!(bool)cedrus_find_format(pixelformat, directions, capabilities); > > > > } > > > > > > I think the original was fine. The return value of cedrus_find_format > > > will be automatically converted to bool before being returned from > > > cedrus_check_format since that is the return-type of the function, and > > > the result of converting any non-zero value to bool is 1. > > > > Okay I was a bit unsure about that and wanted to play it on the safe side > > without really looking it up, but that gave me the occasion to verify. > > > > From what I could find (from my GNU system's /usr/include/unistring/stdbool.h): > > > > Limitations of this substitute, when used in a C89 environment: > > > > - In C99, casts and automatic conversions to '_Bool' or 'bool' are > > performed in such a way that every nonzero value gets converted > > to 'true', and zero gets converted to 'false'. This doesn't work > > with this substitute. With this substitute, only the values 0 and 1 > > give the expected result when converted to _Bool' or 'bool'. > > > > So since the kernel is built for C89 (unless I'm mistaken), I don't think the > > compiler provides any guarantee about bool values being converted to 1 when > > they are non-zero. As a result, I think it's best to be careful. > > > > However, I'm not sure I really see what cocinelle was unhappy about. You > > mentionned single-line functions, but I don't see how that can be a problem. > > It's not a problem per se. I'm just working on a cleanup project for which I > went through all of staging replacing single-line functions with what they > were calling. In some cases that makes it easier to figure out what a > particular function call does, since the called function actually does > something itself instead of just calling a different function? > This function was also flagged as one such potentially-removable function by > Coccinelle; but in order to do the same replacement that I'd done in other > staging drivers, I thought I would do something about the type mismatch > first, especially since find_format doesn't appear to be used anywhere else. > However, now I won't remove check_format and replace it with find_format as > I'd originally planned, since you've said that isn't necessary here. That > leaves the return type issue. > > > > So in the end, I think we should keep the !! and drop the (bool) cast if there's > > no particular warning about it. > > Should I send a version 3 that does this? bool was introduced in C99. Converting a non-zero value to boolean will yield true as a result. Please keep the code as-is; it's much easier to read that way. -- Kind regards, Sakari Ailus _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel